Quoting "Eyepiece": as they say on TV: "This program is brought to you by the Sun... " In fact, so is this website, and just about everything in our world, too! For the energy powering our solar system is provided by Sol, a gigantic nuclear fusion reactor.

Almost every amateur astronomer has had an opportunity to observe sunspots. But lots of solar activity can be seen in the discrete single wavelength radiated by atomic hydrogen, the line of h-alpha light that is visible as a reddish hue of the color spectrum at 656.3 nanometers. At bright levels, the human eye is sensitive to h-alpha light; unfortunately we cannot detect it in dim night sky views. The much stronger levels of h-alpha reaching us from the sun are easily studied, however, provided that the sun's light is greatly attenuated, with the harmful infrared and ultraviolet waves filtered out.

With a hydrogen-alpha solar prominence filter, and proper precaution with a suitable scope, the fascinating display of solar flares and prominences, as well as 'surface' detail, may be safely viewed or photographed.

Sunspots begin as "pores" of cooler gas near the top of individual gas columns, called granules, that extend up through the thin layer of the chromosphere. Small solar pores may last for minutes, but they eventually can spread into gigantic areas, up to 8 times earth's diameter. These sunspots may appear dark, but they are in reality only somewhat cooler than the 5700 Kelvin solar atmosphere (1 K[elvin] = 1° C.) They may last for weeks; complex groups form, and vary in number over an 11-year cycle.

Neutral-density solar filters for a telescope's front aperture are designed to reduce sunlight's intensity some 1 million times. Only then may safe views of the sun be attempted. In the full visible light band, the disk looks yellowish when seen with a glass solar filter. Much h-alpha light is present, but its detail is washed out by irradiation effects. With an h-alpha prominence filter, the viewer may tune in to a narrow range only about a nanometer wide, centered on the h-alpha line.

In h-alpha light such a filter shows huge solar flares, sudden releases of electromagnetic energy from very active regions of the chromosphere. Flares that are seen on the limb of the disk are called prominences: enormous tongues of light that may extend outward for 100,000 miles, and even further: occasionally as far out as nearly the 862,400 mile diameter of the Sun. Powerful magnetic fields may pull them back to the surface; they can curve, spray, and assume an infinite variety of shapes and sizes. Occurrences follow the frequency of sunspots, but often flare up late in the cycle. Distinct changes may be detected over just a few minutes!

PICTURE NO. 1 (left): Ron Wood obtained this color exposure using Kodak 100, a Celestron 70mm fluorite scope, and a neutral-density solar filter.

PICTURE NO. 2 (middle): Solar prominence, viewed in h-alpha light and drawn by Steve Waldee, made late in the solar cycle that ended in the mid-1990s. The telescope was a 10-inch aperture Newtonian reflector, stopped down to 77 mm of aperture, using a Lumicon 1.5-Angstrom solar prominence filter system; a sunspot is visible, but so is a gigantic prominence that has extended over a large region of the circumference.

PICTURE NO. 3 (right): An image made on Sept. 14, 1999 by the spacecraft SOHO (credit: NASA) taken in the 304 angstrom wavelength, and processed in false color. The original webpage may be found here, with more information about this picture.

Safe Solar Observing: Hydrogen-Alpha Solar Prominence Study